Abstract 45: Interleukin-19 Increases Angiogenic Gene Expression and Perfusion in Ischemic Hind-Limbs

Abstract

Introduction: Peripheral vascular disease affects over ten million Americans. Hypoxia in ischemic limbs typically initiates angiogenic and inflammatory factors to promote angiogenesis in attempt to restore perfusion. Little is known about the inflammatory nature of angiogenesis particularly with respect to anti-inflammatory factors. Interleukin-19 is a uniquely anti-inflammatory Th2 cytokine that promotes angiogenesis in cellular assays. We hypothesized that IL-19 could drive angiogenesis in vivo; the purpose of this study is to characterize a role for IL-19 in restoration of blood flow in the hind-limb ischemia model, and define potential mechanisms. Methods and Results: Three complimentary experiments were designed to clarify IL-19’s angiogenic role. 1- C57BL/6 (n=12) were subject to induced hindlimb ischemia by femoral artery ligation and subject to daily i.p. injections of recombinant mouse IL-19 (10ng/g/day) or PBS for 14 days. Mice were subsequently imaged using Laser Doppler Perfusion Imaging (LDPI). Perfusion index was evaluated by comparing values between ligated and unligated contralateral limbs. C57BL/6 mice injected with rIL-19 showed significantly increased levels of perfusion when compared to PBS injected age-matched cohorts (p<0.01 at day 7, <0.05 at day 10). 2- hindlimb ischemia was similarly induced in both C57BL/6 and IL-19-/- mice on a C57BL/6 background. LDPI values are significantly decreased in IL-19-/- mice when compared to C57BL/6 mice (p<0.05 at day 7). 3- IL-19-/- mice subject to limb ischemia were given daily i.p. injections of rIL-19 or PBS. IL-19-/- mice administered rIL-19 trended (P=0.058) higher perfusion when compared to PBS injected control mice. Immunohistochemistry using CD31 antibody on adductor muscle recovered from these mice showed significantly increased capillary density in IL-19 treated mice compared with controls (P<0.05). cDNA microarray analysis of human microvascular endothelial cells treated with IL-19 determined increased expression of angiogenic cytokines, which was verified by qRT-PCR and western blot. Conclusions: This study is the first to implicate IL-19 as a novel pro-angiogenic cytokine with potential to promote neovascularization and restore blood flow in ischemic tissue.